The goal of this prospective longitudinal study is to examine the etiologic determinants of changes in tobacco use in a sample of South African adolescents. The proposed sample includes 750 black and 750 white adolescents ages 12-17 at Time 1. The study will attempt to: (1) identify the risk and protective factors that can affect South African adolescents' tobacco use; (2) examine the interrelations and interactions of personality, family, peer, ecological context, tobacco context, and cultural factors as they affect the course of tobacco use (i.e., stability, change) and nicotine dependence in a sample of South African adolescents; (3) examine the relationship between early tobacco use and later adolescent functioning; and (4) establish an infrastructure for tobacco research in South Africa. Individual interviews with the subjects will be conducted by trained interviewers at two points in time. Scales with adequate psychometric properties measuring the independent variables will be developed. The primary analytic techniques will be LISREL, hierarchical, and logistic regression. The significance of this study lies in: (a) its longitudinal design with in-depth, intrapersonal, interpersonal, cultural, and problem behavior data available on South African youth; and (b) strengthening the research base in both the United States and in South Africa. This is the first time this type of data will be available for South African adolescents, especially for so large a sample at particular risk for tobacco use. Knowledge of the risks for tobacco use, and the consequences of tobacco use for functioning are important for determining the foci and timing of effective prevention and treatment programs. A major focus will be on capacity building and developing an infrastructure in South Africa. Our research will also focus on developing a fuller understanding of cultural factors which is critical for establishing effective prevention and treatment programs to deal with growing problems due to tobacco use.